Tennis balls and their coverings



Sept. 13, 1960 E. BUKALDERS ETAL 2,952,053

mums BALLS AND THEIR COVERINGS Filed Aug. 15, 1956 2 Sheets-Sheet 1 -FIG. 7.-

INVENTORS 2, M W, p4, M M 1 Sept 1960 E. BUKALDERS ETAI. 2,952,063

mums BALLS AND THEIR COVERINGS 2 Sheets-Sheet 2 Filed Aug. 13, 1956 TENNIS BALLS AND THEIR COVERINGS Edwards Bukalders, Barnsley, Harvey R. Chadwick,

Horbury, John Ogden, Mossley, Eric B. Gibson, Old- .ham, and Geolfrey Greaves, Stalybridge, England, assignors t Slazengers Limited, London, England Filed Aug. 13, 1956, Ser. No. 603,475 7 Claims priority, application Great Britain Aug. 17, 1955 Claims. CI. 28-72 This invention relates to the manufacture of playballs of the kind comprising a resilient core with a fabric covering" and aims to improve the wearing qualities of such covers. I e n '-It is convenient in this specification to describe and distinguish this invention by reference to, and comparison with, conventional methods of manufacturing and covering tennis balls, but although the invention is particularly' directed towards improving the wearing quality of tennis ball covers, it is also equally applicable to any other fabric-covered play-ball. References in the specification, therefore, to tennis ball manufacture are not to be construed as limiting the invention to tennis balls only. The rough surface or nap of an unworn tennis ball is essential for good play, since it enables skilled players to exercise greater control over the ball. Nevertheless, the cover of a tennis ball rapidly deteriorates during play, particularly on hard courts.

The" method most commonly employed in tennis ball manufacture at the present time is to form an inflated core'of rubber and to cover the core by applying panels of'a fulled and felted textile cloth, such for example as melton, suitably treated to provide a nap finish. Normally, two substantially identical panels of figure-8 or dumb bell shape, are employed for each ball.

In'theproduction of melton cloth it is customary to use'nat'ural fibres; normally these are wool fibres. In some cases, a woollen weft and a cotton warp are used. 2 The woven cloth is dense, and in finished form hasa relatively 'rough surface or nap. "After initial weaving, the'cloth is subjected to a carding or similar operation to raise the fibres on one surface of the woven cloth. Next a milling and fulling operation is carried out; usually this is a chemical and mechanical treatment which both shrinks the weave to densify the cloth, and also causes the raisedsurface fibres themselves to shrink and to become felted or entangled, resulting in a rough closely felted surface.

Panels are then cut from this cloth and secured to the 'core, usually with an adhesive which requires both heat andpressure. This step tends to flatten the surface fibres closely against the ball, and therefore, a final steaming: or other raising operation is generally performed to lift the fibres again and produce the final nap. For many years, nothing but natural fibres have been used in-tennis ball;cover fabric, but, with the development of synthetic organicfibre-forming plastics, it has been found .possibleto improve the wearing qualities of natural fibres by the addition, in the weave of the melton c lotl'1, ;of a minor percentage (not more than 45%) of synthetic organic thermoplastic or other synthetic fibres, hereafter for convenience termed synthetic fibres). An example of such a cloth is described in British specification No. 629,484., p p It is possible closely to control many of the properties of synthetic fibres, and particularly of polyamide or polyesterlfibres, during their manufacture. For example,

the strength, resilience, denier and staple length of synthetic fibres and monofilaments can all be predetermined, and the resultant products can be made stronger and more resilient than wool fibres of equivalent denier and staple length. So far as surface characteristics are concerned however, wool fibres have a scaly surface, whereas synthetic fibres tend to have a smooth and relatively slippery surface.

The mixture of such synthetic fibres with natural.

fibres in a textile fabric results in a more durable fabric. Difliculty arises, however, if there is too great an inclusion of synthetic fibres in normal tennis ball cloth, or if such fibres are of substantial denier, say 10 or more. This difiiculty is four-fold.

In the first place, the normal adhesives (such as rubbersolution or latex) which are used to secure the natural fibres of melton cloth to rubber, will not satisfactorily join synthetic fibres to rubber. Whilst it is not impos- 1 a perpendicular pile), whilst the opposite or back 'sur-- sible to provide alternative adhesives which will join synthetic fibres to rubber, it has been found that the use of such special adhesives involved further treating the synthetic fibres before the application of the adhesive, thus involving an extra step in manufacture. For this reason, if the covering fabric is predominantly synthetic, tennis ball manufacture becomes more expensive and complicated. p

In the second place, the majority of synthetic fibres are not afiected by chemicals ordinarily used in a fulling operation on melton cloth. Hence, if a milling or fulling operation is attempted on a fabric in which synthetic fibres greatly predominate over natural fibres, little, if any, shrinkage or densification will normally result.

Thirdly, synthetic fibres cannot, according to present methods, be felted, so thatthe desired entanglement cannot be produced.

Fo urthly, there is a limit to the denier size of the synthetic fibres which can be used successfully with natural fibres.

Thus, although the addition of synthetic fibres is highly desirable to increase the wearing properties of the tennis ball cloth, it involved peculiar difiiculties and the quantity and denier size of synthetic fibres which can be included in the normal milled and raised cloth is severely limited;

It is not only desirable that the ball covering should have a relatively rough surfacebut that it should retain a uniform roughness throughout its playing life.

With tennis ball coverings having a milled or fulled surface, during use, the surface fibres are disturbed and broken by abrasion and as this 'does not occur evenly it is impossible to retain'the uniform required roughness or nap and thus required playing characteristics. When synthetic fibres are included it has been found the denier size is important in-that such size must be relatively small so that said fibres can also break off with the other, natural, fibres. Experiments have shown that synthetic fibres of, say, ten or more denier are so"rela tively stronger than natural fibresthat a ball after use has long synthetic fibres overlaying and/or projecting from its playing surface. It would be an advantage to use these thicker synthetic fibres forreinforcing the covering, but the above problem hasto be solved.

Covering materials for play-balls are known which overcome certain difiiculties and which comprise pile fabric material in which the pile threads consist largely of synthetic fibres, while the threads of the base weave consist wholly or mainly of natural fibres.

By the term fpile fabric is meant a fabric in which certain selected threads (called pile threads) in the fabric are so woven as. to extend outwardly from the Patented Sept. 13, 1960,

. face is a woven textile surface in which continuous warp and weft threads interlock without their ends being exposed on the surface.

We have now found that it is possible to modify the existing methods of manufacture of tennis ball cloth, so as to produce an improved ball covering cloth which, although not woven as a pile fabric with specific pile threads, nevertheless possesses on the surface, certain of the characteristics of a pile fabric, and, in addition, has advantages of texture exceeding those of the nap of normal melton cloth and not possessed by a perpendicular pile fabric. Moreover, our improved ball covering cloth can readily be made with any desired quantity of synthetic fibres on the playing surface, varying from zero up to and including 100%.

According to the present invention there is provided a method of manufacturing a ball covering cloth in which the playing surface is constituted by a random pile (as herein defined), which includes the steps of weaving a fabric from spun yarns; raising the fibres on one surface of the fabric so as to produce an overlay of long fibres which extend at varying angles away from their parent threads, and cropping the long fibres of the overlay. I

By the term random pile in this specification we do not mean a pile fabric of the kind earlier defined herein. We mean a normal textile fabric being either a woven textile fabric with warp and weft threads, or a knitted fabric, in which the surface threads have initially been made up from twisted yarn from staple fibres, and in which the raising operation has resulted in a partial unravelling of these surface fibres, so that, after cropping, they extend in differing directions for a relatively short distance outwardly from their parent thread at substantially all radial angles within an arc of about 180, depending upon the angle at which any particular fibre has emerged from the twist of its parent thread when unrevelled by the raising operation.

If desired, after the surface fibres have been raised, and before they are cropped, the said fibres may be subjected to a piling operation to cause them to assume an upstanding disposition without any nap effect.

The term piling should be understood to mean that the fabric is subjected to a treatment which causes the fibres to assume an upstanding disposition without any nap effect. In a raising operation, the fibres normally have a slight nap in one direction, and are not separated to the same degree as they are when they have been piled.

The degree of raising the surface fibres decides, at least to a large extent, the density of the resulting random pile surface and cropping is carried out to a degree to suit requirements. Thus the raised fibres, preferably after piling, may be cropped short, or to a medium length, or be relatively long, but in all cases the fibres are, as reasonably as possible, of even depth from the inner face of the base weave.

The invention further includes a covering fabric or cloth for tennis or like play-balls made by the method aforesaid, and also a tennis or other play-ball covered with such fabric.

The surface texture of a random pile of this nature is far superior to the nap of a normal melton cloth.

By the use of normal weaving techniques in which selected warp or weft threads predominate on the playing surface of the material (as for example has been described in prior British specification No. 629,484), it is possible to include in such thread and hence on such surface, any desired concentration' of non-feltable synthetic fibres up to and including 100%, so that all the advantages of such fibres over natural fibres can be employed. In some cases there is no necessity for surface felting which enables high concentrations of non-feltable synthetic fibres to be used but in such cases cropping is to greater extent to produce relatively short fibres.

In some circumstances, however, it may be found advantageous to employ a high concentration of natural fibres in the random pile and, after cropping, preform a light milling or fulling operation upon the fabric which will serve to give the fabric a slightly more conventional appearance. In such cases the fibres may be cropped as aforesaid to a medium length.

Alternatively, it may be desirable to perform what may be termed heavy milling or fulling operation upon the fabric and in this instance it is desirable to leave the fibres, when cropping, relatively long as before stated.

It should be appreciated that the milling or fulling operation above referred to may be carried out on the fabric before it has been afiixed to the ball core, or in some cases, after such fixing-has been completed.

It is also possible that in certain cases, the, or a further, cropping operation is carried out upon the covering fabric when this has been fixed in position upon the ball.

In some cases, the fibres which are to be raised and cropped to form the random surface pile of a cloth according to this invention may be made from yarns consisting entirely of synthetic fibres.

Alternatively, such threads may be made from yarns composed of a mixture of synthetic fibres," and natural animal or vegetable fibres such as wool, cotton or wool and cotton.

Thirdly, such threads may be made from yarns consisting entirely of natural fibres.

The quantity of synthetic material in the pile may be closely controlled, and any quantity varying from 0% up to and including of synthetic fibres, and from 0% up to and including 100% of natural fibres may be included in the random pile. Moreover, the denier size of the synthetic fibres may be greater than that able to be used in normal woven coverings, say in the order of having apercentage of synthetic fibres, it is desirable to arrange for a high concentration of such synthetic fibre on the playing surface of the cloth, and relatively few picks of the threads containing synthetic fibres will be exposed on the underside of the cloth. In this way, a

predominance of natural fibres can be secured on the underside which enables normal adhesives to be used.

Preferred forms of synthetic material to be employed, when desired, in the random pile of the playing surface, are polyamide or polyester. If desired, a mixture of these materials may be employed with each other or with natural fibres.

' The manufacturer of tennis ball cloth in accordance with the present invention is distinguished from previous normal methods of producing melton cloth by the fact that, after weaving or knitting the fabric and raising the fibres on one surface, the step of milling or fulling which normally follows at this stage, to entagle the raised surface fibres, is omitted, and the step of cropping is introduced.

Because it is intended to crop these raised fibres to produce a short, random pile it is clearly undesirable to entangle them by milling before any cropping takes place.

It has already been suggested that in certain cases where natural fibres predominate, it may be desirable to carry out a milling or falling operation and, apart from producing a slightly more conventional appearance, this will produce a shrinkage or densification of any natural fibres, particularly wool fibres, present in the material.

A preferred embodiment of the invention will now be described with reference to the accompanying drawings in relation to the manufacture of a tennis ball: in which 5. the covering cloth has a random pile, with a high percentage of synthetic fibres in the pile.

Fig. 1 shows a tennis ball having a covering formed from two figure 8 panels with a random pile playing surface;

Fig. 2 is an enlarged sectional detail view of a piece of woven fabric after a raising operation;

Fig. 3 is an enlarged sectional detail view of a piece of woven fabric after raising and piling operations;

Fig. 4 is an enlarged sectional detail view of a piece of woven fabric after raising and piling operations and including three alternative cropping levels;

Fig. 5 is an enlarged sectional detail view of a piece of woven fabric after the cropped fibers have been milled and fulled down; and

Fig. 6 is a diagrammatic side elevation of a machine for piling and cropping a tennis ball fabric.

A cotton warp is employed and a weft comprising mixed wool and nylon yarn is also employed. For example, the fabric is woven from 100% cotton warp yarn and a weft yarn composed of: crossbred wool 85%, nylon yarn 15%. The weaving may be carried out on a loom having two or more shafts, and the cotton warp is arranged to form the greater part of the back 2 of the fabric whilst the mixed wool and nylon weft forms a greater part of the front 3 of the fabric.

After scouring, the weft is raised as shown in Fig. 2, for example on a single or double action raising machine, having wire covered rollers, and the raising operation is carried out to a required degree. This will give an appreciable flutfy fulness to the front of the fabric and produce an overlay of long fibres 4 of uneven length which may be a quarter of an inch or more in length, such fulness being due to the mass of fibres which are brought up by the action of the raising machine. As will be understood from the foregoing, the length of the raised fibres 4 illustrated in Figures 2 and 3 has been exaggerated in the interest of affording a ready understanding of the invention.

The next operation is the piling of the raised fibres 4 and then the cropping of the upstanding fibres 4a which may conveniently be carried out on a single machine. Fig. 3 illustrates broadly the eifect of piling of the fibres 4 which attain a more upstanding position 4a, thus ensuring a more even surface level and length of fibre when cropped. As shown particularly in Fig. 4, the upstanding piled fibres may be cropped to different levels according to final requirements. For example, the fibres may be cropped short to a level such as that indicated by line 5 and in this instance the cropped fibres will form :a random pile without the necessity for a further operation such as a milling operation. Alternatively, the fibres may be cropped to a medium length such as that indicated by cropping line 6 and in this instance the cropping operation may be followed by a light milling operation at a convenient or required stage in the manufacture of the covering. In a third method the pile fibres are cropped on say a line 7 so as to give a relatively long fibre and in this instance a so-called heavy milling operation is carried out to produce a playing surface 4b of entangled fibres as shown in Fig. 5. All these three arrangements are capable of producing a random pile playing surface.

The machine, as shown in Fig. 6, consists of a frame 8 and the necessary driving means (not shown) for the various operative parts. The fabric 9 is first led beneath a guide roller 10 and then over a brake roller 11. It then passes from front to back of the machine, its raised surface coming, during the travel, under the influence of a beater 12. The fabric next passes in vertical direction over guide rollers 13, 14 and is then moved forward to a piling edge 15, disposed transversely of the machine making a 90 turn at the edge, which operates against the periphery of an adjustable roller 16 with the fabric passing therebetween. The edge is mounted in a micrometer assembly 17 to give fine" adjustment, according to the depth of pilerequired at Finally, the fabric 9 passes upwards and? trol the final pile depth. Y

A similar result may be obtained by piling and cropping the cloth on a conventional cropping machine, by means of a wire brush attachment, which operates on the surface of the nap thus piling the fibres in preparation for cutting;

The piling operation may be carried out in some other manner than by the use of the aforesaid mechanical means, e.g. an electrostatic piling operation may be em-.

ployed. By this it is intended that the fabric after a raising operation, is submitted to an electrostatic field so that the raised fibres are attracted in a manner that will cause them to be upstanding to a required degree for the cropping operation. Conveniently the cutter itself, such as a multi-bladed rotary cutter, is adapted to form one electrode and thus the fibres will be attracted towards the blades into the required upstanding arrangement and thus be cropped according to requirements. Alternatively, the electrostatic field creating means may be arranged immediately in advance of the cutting means such as by the positioning of an electrode over the raised fibres and in close proximity to the cutting means.

If found advantageous, mechanical and electrostatic piling operations may be employed in conjunction to facilitate the piling of the fibres. In this case it is preferred to arrange the electrostatic piling to follow the mechanical piling, i.e. carry out the electrostatic piling operation during or immediately prior to the cropping operation.

After the manufacture of the random pile surfaced fabric, the shaping of the cover panels and the covering of the ball core may be carried out by known methods.

The cover panels may be formed in the conventional manner by cutting out flat panels, for example, figure-8 panels, as applied in Fig. 1, from the sheet of fabric, or by cutting and moulding from the sheet hemispherical cups having the pile fibres extending outwardly at random away from their convex surfaces.

The attachment of the panels or cups to the core may also be carried out in the known manner, using either an adhesive which sets under heat and pressure or a cold setting adhesive.

Any suitable adhesive may be used, such as rubber solution or latex, both of which are cured under heat and pressure, or a cold-setting flexible resin such as polyester isocyanate resin. The latter is less liable to discolour any synthetic fibres such as nylon present in the fabric.

The treated panels are then applied to a rubber core which has been made by known moulding methods, and the adhesive is caused to set by the application of pressure, and where necessary, of heat also.

It is customary to make the butt joint between the covering panels or cups as close as possible, and to employ adhesive not only between the covering and the core, but also between adjacent edges of the panels or cups.

If the moulding operation employed to press the cover closely around the core tends to flatten the fibres of the pile, these may be raised by known methods such as carding or teazling or steaming.

What we claim is:

l. A method of manufacturing a tennis ball, which includes the steps of forming a textile or a knitted fabric for the covering material from spun yarn; raising the fibres on one surface of this fabric, thereby producing an overlay of long fibres on this surface; cropping these long fibres to an even level, to produce, or facilitate the production of, a random pile (as herein defined); cutting from the said material panels to form the ball cover and fixing thesaid panels to a resilient ball core by means of a suitable adhesive, the pile surface being outermost to form the playing surface.

2. -A method of manufacturing a ball covering, cloth as claimed in claim 1, wherein, after the surface fibres have been raised, and before they are cropped, the said fibres are subjected to a piling operation to cause them to assume an upstanding disposition for more uniform cropping.

3. Method according to claim 1, wherein the fibres are cropped to a short length.

-4. Method according to claim 1, wherein the fibres are cropped to a medium length and subsequently submitted to a light milling or ful'ling operation.

5. Method according to claim 1, wherein the fibres are cropped to a relatively long length and subsequently submitted to a heavy milling or fulling operation.

References Cited in the file of this patent UNITED STATES PATENTS 1,146,125 Bogani July 13, 1915 1,593,21 1 Faulkner et a1. July 20, 1926 1,991,534 Wood Feb. 19, 1935 2,163,674 Gentle June 27, 1939 2,300,062 Radford Oct. 27, 1942 2,479,478 Day Aug. 16, 1949 2,704,877 Schmidt Mar. 29, 1955 FOREIGN PATENTS Great Britain Jan. 8, 1940 

